Knocking in shower valve

Discussion in 'General Plumbing Help' started by tony14, Dec 11, 2010.

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  1. Dec 11, 2010 #1

    tony14

    tony14

    tony14

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    The shower valve in the kids' bathroom gives a kind of double knocking sound when water is turned on or off in the house, particularly when the clothes washer or dishwasher do their on-off thing.

    This happened several years ago. I tried installing an air column here, a knock arrestor there, but nothing helped until we redid that bathroom and put in new shower hardware, which cured it completely.

    Now the knocking has returned, and I assume we will need to break into the wall and replace the shower valve again. The second unit was a different make and model than the first. Can anyone explain to me what went wrong with these valves, and how we might avoid it in the future? We do have hard water, if that could be a factor.
     
  2. Dec 11, 2010 #2

    havasu

    havasu

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    Maybe a washer loosened up in the valve?
     
  3. Dec 11, 2010 #3

    phishfood

    phishfood

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    What brand of shower valve did you install when you remodeled?

    Here is a page on water hammer arrestors that shows several types. Oops, forgot to insert the link. Here it is:http://www.plumbingsupply.com/waterhammerarresters.html One of these is intended to be attached directly to the washing machine box, and if the washing machine is one of the main culprits, putting these on could help. It is a little more difficult, but if you don't have one on the dishwasher, you can install one there as well. But you mentioned that you tried some hammer arrestors when you originally noticed the problem. Did you put in "job made arrestors", basically vertical pieces of pipe with a cap on the top, or did you install commercially made arrestors?

    Since the noise is coming from the shower valve area, it is possible that you have a loose pipe in that area that is banging against something. When you remodeled, how much of the supply piping to the valve did you expose and inspect?
     
    Last edited: Dec 11, 2010
  4. Dec 11, 2010 #4

    SlowDrip

    SlowDrip

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    The most common culprit in the shower area is indeed a loose pipe as phishfood suggests, usually the line to the shower head is not secured properly. Try pushing/pulling your showerhead gently, there should be no forwards and backwards movement.
     
  5. Dec 12, 2010 #5

    tony14

    tony14

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    I listened carefully when my wife started a load of wash and the noise does seem to be coming from the shower valve area. The shower head did not move at all.

    I don't recall the brand it is. Can something indeed come loose inside the control unit, like a washer as havasu suggested, or wear, or get crudded up? If so, are there rebuild kits if it is a common type? I'm wondering if I can disassemble it and take the innerds to a hardware store, or Home Depot where I got it.
     
  6. Dec 13, 2010 #6

    phishfood

    phishfood

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    Depending on the valve, it is possible for parts to work loose and cause problems. However, I would expect the problem to present itself when the shower itself is used, not when other fixtures are in use.

    Yes, there are rebuild kits available for many of the more popular valve models. Sometimes it is possible to take the valve apart and fix it without replacing parts, like the Kohler that I fixed for my mother this morning. Other valves, it is pretty much a matter of replacing the cartridge, period.
     
  7. Dec 13, 2010 #7

    tony14

    tony14

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    I've attempted to attach a snapshot of the valve. Can anyone tell the maker by looking at it?

    shower_valve_002_sm.jpg
     
  8. Dec 13, 2010 #8

    SlowDrip

    SlowDrip

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    Hrm, not sure of the make but I can make some semi-educated guesses as to how it comes apart.

    [​IMG]

    The black part (circled in red) should unscrew counter-clockwise. You may need to grip it with pliers or a wrench, if so use a cloth or cardboard to make sure that you do not damage the outer threads.

    The white part (circled in green) is your cartridge and should pull straight out after removing the black plastic ring. Make sure the water supply to the shower is shut off before doing this. Once removed you can either post a picture of the cartridge here and we can attempt to identify it for you, or take it to your local plumbing supply and they should be able to help.

    There is a buildup of something on the hot water supply pipe (circled in blue) that looks suspiciously like lime or calcium from hard water. It is hard to tell from a picture. If this IS a scale buildup it may mean you have a slight leak from where that MIP is soldered to the pipe. It is possible that it is just drywall mud or grout or something similar dropped on the pipe from finishing one of the walls.

    Lastly, it appears as if your shower valve and the supply pipes are just kind of "hovering" instead of being attached to anything. This could cause the valve to shake when water enters it, which could be causing your knock. While you have everything exposed, turn the shower on with a pair of pliers and see if you notice a slight thud or shaking around the valve.
     
  9. Dec 13, 2010 #9

    tony14

    tony14

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    Thank you very kindly for the comments and instructions! There's nothing like a picture to move things along, eh?

    Another question: I am assuming this is a 'pressure balanced' unit, because its installation several years ago solved a longstanding problem of the shower running hot or cold when other faucets were used. Is the pressure balancing function inside the white cartridge, or is it another part that may have to be replaced elsewhere in the unit?
     
  10. Dec 14, 2010 #10

    phishfood

    phishfood

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    I THINK that you have a Price Pfister valve. If I am correct, you will need to shut the water off, drain the pressure, unscrew the 4 Phillips screws on the metal collar, and pull the cartridge out by grabbing the white stem with pliers and pulling away from the wall.
     
  11. Dec 14, 2010 #11

    tony14

    tony14

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    Yes, that's it, it is a Price Pfister. Thanks.
     
  12. Dec 20, 2010 #12

    tony14

    tony14

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    I would like to replace the value unit and asked the manufacturer via their website what model line it is, several days ago no answer yet. Can anyone suggest which valve (part number, model line, etc) would be the correct replacement? Here is what it looks like inside and out. It's about 7 years old.

    External-Internal.jpg
     
  13. Dec 20, 2010 #13

    SlowDrip

    SlowDrip

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    Hrm, not a pfister I am familiar with, but I have only been selling them for about 9 months and don't have the background I have with other manufactureres

    If i had to guess, I would say it is the OX8, which is discontinued. You may still be able to find them in plumbing supply shops if you are lucky. I do know that that pfister is a pain in the ass to deal with, I would be surprised if they ever got back to you.

    If you are thinking of replacing the valve, though, you can really do whatever the heck you like. The valve is the main part of the unit, everything else is just trim. When you buy a shower unit about 80% of the cost is actually the valve (unless you are getting some fancy unit)
     
  14. Dec 20, 2010 #14

    tony14

    tony14

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    I misspoke. I don't want to replace the whole valve, just the working part that's held the housing by the four screws. I'm not sure how to refer to it.
     
  15. Dec 21, 2010 #15

    phishfood

    phishfood

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    The "inner workings" of the valve is called the cartridge.

    Unfortunately, I don't know what part number you will need. I would try pulling the cartridge and taking it to your local big box or hardware store and trying to match it up.
     
  16. Dec 21, 2010 #16

    tony14

    tony14

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    To be honest, I was wondering whether to get officially annoyed with Price Pfister--it had been a few days since I messaged them. Well, they answered today and told me they are sending me the parts under warranty! I hadn't even asked for that, all I had asked for was help identifying which parts they were! Here is the text:

    "Thank you for your recent email describing the difficulties you are experiencing with your unit. We apologize for the inconvenience.

    The parts necessary to repair your unit are being ordered for you at no charge under our product warranty, based on the model number provided. They should arrive within 7-10 working days.

    The valve model number : 0x8-310a
    the cartridge needed part # 974-042

    Thank you for choosing our product(s) and for giving us the opportunity to be of service to you."

    This faucet is about seven years old and and probably no longer made. They definitely deserve an attaboy for that. I thought lifetime warranties were only Grohe's thing. Thanks everyone for the assistance so far. I will report back when I get the new parts installed.
     
  17. Dec 21, 2010 #17

    SlowDrip

    SlowDrip

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    Most major manufacturers have a lifetime warranty. delta, Moen, pfister etc...

    If for whatever reason Pfister sends the wrong part, take your old one in to the closest Lowe's and they should have free warranty replacement cartridges at the pro desk for you. Other retailers may or may not have warranty replacements onhand.

    Hope it all works out.
     
  18. Jan 7, 2011 #18

    tony14

    tony14

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    Regarding my original post which began this thread:

    "The shower valve in the kids' bathroom gives a kind of double knocking sound when water is turned on or off in the house, particularly when the clothes washer or dishwasher do their on-off thing..."

    I replaced the cartridge with the one sent to me by Price Pfister (part #974-042, I believe) and haven't heard the knocking noise since. Odd perhaps, but there you have it.
     
  19. Jan 7, 2011 #19

    SlowDrip

    SlowDrip

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    Glad to hear things worked out.
     

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